Modified Maleimide Oligomer, Preparation Method Thereof and Composition Containing the Same

ABSTRACT

A modified maleimide oligomer is disclosed. The modified maleimide oligomer is made by performing a reaction of a compound having a barbituric acid structure, a free radical capture, and a compound having a maleimide structure. A composition for a battery is also disclosed. The composition includes the modified maleimide oligomer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Taiwanese Patent Application No.101148939, filed on Dec. 21, 2012, the disclosure of which is herebyincorporated by reference herein.

TECHNICAL FIELD

The disclosure relates to a modified maleimide oligomer for a battery, amethod for preparing a modified maleimide oligomer and a compositioncontaining a modified maleimide oligomer.

BACLGROUND ART

Recently, 3C electronic devices such as notebook computers, folding cellphones, digital cameras and the like are developed to be lighter,thinner, shorter and smaller, which has become the trend of developmentof electronic technique and communication devices and further increasedthe demand for a “secondary battery” as a portable power supply.Accordingly, secondary batteries have been also developed to be thinner,smaller and lighter. Meanwhile, the requirement of capacitance of asecondary battery is increased in response to the need of electronicdevices with multifunction, high speed, high performance and high power.

Generally, a lithium ion battery has an energy density about 260 to 270kWh/m³, which is about 2 folds or higher of the energy density of anickel-cadmium alkaline secondary battery. Lithium ion/lithium-polymersecondary batteries have the advantages such as rapid charging rate,high discharging power and high energy density, so that lithium ionbatteries and lithium-polymer batteries have played important roles inthe application of small-scaled electronic devices among all secondarybatteries. However, there still is a need to focus on safety,capacitance and cycle life at high temperature and high pressure forbatteries in battery industry and electric vehicles.

SUMMARY

The disclosure provides a modified maleimide oligomer for a battery. Themodified maleimide oligomer is produced by reacting a compound having abarbituric acid structure, a free radical capture and a compound havinga maleimide structure, wherein the reaction mole ratio of the compoundhaving he maleimide structure to the compound having the barbituric acidstructure is in a range from 25:1 to 1:1, and the reaction mole ratio ofthe compound having the barbituric acid structure to the free radicalcapture is in a range from 1:1 to 1:0.1.

The disclosure further provides a composition for a battery. Thecomposition includes an active material; a conductive additive; abinder; and a modified maleimide oligomer in the amount of 0.1 to 5 wt %based on the total weight of solid contents in the composition.

DETAILED DESCRIPTION OF THE INVENTION

Hereafter, the disclosure will be explained in detail with the referenceto certain examples, those skilled in the art can readily understandother advantages and effects of the disclosure according to the contentsdescribed in the description.

The modified maleimide oligomer for a battery provided by the disclosureis produced by a partially free radical ring-opening reaction of acompound having a barbituric acid structure, a free radical capture anda compound having a maleimide structure.

In one embodiment, the reaction molar ratio of the compound having themaleimide structure to the compound having the barbituric acid structureis in a range of from 25:1 to 1:1.

The reaction molar ratio of the compound having the barbituric acidstructure to the free radical capture is in a range of from 1:1 to 1:01

The compound having the barbituric acid structure used in the disclosureis a compound of formula (I):

wherein X, Y and Z are all oxygen atoms or at least one of them isreplaced with a sulfur atom, and each of R₁, R₂, R₃ and R₄ isindependently hydrogen or C₁₋₅alkyl.

In one embodiment, X, Y and Z are all oxygen atoms, both R3 and R4 arehydrogen, and R₁ and R₂ are independently hydrogen or a C₁₋₅alkyl,provided that R₁ and R₂ are not hydrogen at the same time.

In a further embodiment, at least one of X, Y and Z is replaced with asulfur atom, and R₁, R₂, R₃ and R₄ are independently hydrogen orC₁₋₅alkyl.

The modified maleimide oligomer of the disclosure can be used as anadditive in cathode plate slurry, insolating film and electrolyte of abattery such as a lithium ion battery, and the additive contains acompound having a barbituric acid structure which trends to generatefree radicals, so that the conductivity would be affected by theexcessive free radicals which catch lithium ions. Thus, the modifiedmaleimide oligomer provided in the disclosure is made with the use of afree radical capture, wherein the free radical capture is at least oneselected from the group consisting of hydroquinone, α-tocopherol,bisphenol-A, phenol, p-benzoquinone, 1,4-dihydroxynaphthalene,p-methoxyphenol (MEHQ), dodecanethiol, butanethiol, carbontetrachloride, carbon tetrabromide, catechol, resorcinol,methyl-hydroquinon, trimethylhydroquinone, tert-butylhydroquinone and2,5-di-tert-butyldroquinone.

The compound having a maleimide structure used in the disclosure mayhave a dimaleimide structure and/or a monomaleimide structure.

In one embodiment, the compound having a maleimide structure is acompound of formula (II):

wherein each of m, n and o is an integer greater than 1.

In another embodiment, the compound having the maleimide structure is acompound of formula (III):

wherein R is C₁₋₁₂alkylene,

In one embodiment, the C₁₋₁₂alkylene may be —(CH₂)₂—, —(CH₂)₆—,—(CH₂)₈—, —CH₂)₁₂— or —CH₂—C(CH₃)₂—(CH₂—CH(CH₃)—(CH₂—.

In still another embodiment, the compound having the maleimide structureis at least one selected from the group consisting of followingmonomaleimides: Phenylmaleimide, N-(p-methylphenyl) maleimide,N-(o-methylpheyl)maleimide, N-(m-methylphenyl)maleimide, N-cyclohexylmaleimide, maleimide, maleimidophenol, maleimidobenzocyclobutene,phosphorus-containing maleimide, phosphonate-containing maleimide,siloxane-containing maleimide,N-(4-tetrahydropyranyl-oxyphenyl)maleimide and 2,6-xylyl-maleimide.

For example, propylene carbonate (PC) or N-methylpyrrolidone (NMP) canbe used as a solvent in the modification, wherein the ratio of the totalweight of the compound having the barbituric acid structure, the freeradical capture and the compound having the maleimide structure to theweight of the solvent is within the range from 3:97 to 40:60. Themodification can be performed at the temperature from 110° C. to 130° C.for 2 to 7 hours.

The modified maleimide oligomer has a dendrimer-like hyperbranchedstructure which can form a stable complex compound with an electrodeactive material such as metal oxide in the electrode slurry to increasedispersibility, to reduce viscosity of the slurry, and to maintain thestable viscosity for long time.

In one embodiment, the disclosure provides a composition for a battery.The composition includes an active material; a conductive additive; abinder; and a modified maleimide oligomer in an amount of 0.1 to 5 wt %based on the total weight of the solid contents in the composition,wherein the active material is a cathode active material or an anodeactive material.

When used as an electrode slurry composition, it can be used in thefabrication of a cathode film of a lithium ion battery or alithium-polymer battery. In the fabrication of a cathode film, a cathodeactive material, for example, at least one selected from the groupconsisting of lithium nickel cobalt aluminum (NCA), lithium nickelcobalt manganese (LNCM), lithium cobalt oxide (LiCoO₂), lithiummanganese oxide (LiMnO₂), lithium nickel oxide (LiNiO₂) and lithiumferric phosphate oxide (LiFePO₄) is used as the electrode activematerial in the slurry composition. On the other hand, an anode materialsuch as at least one selected from the group consisting of mesophasecarbon microbeads (MCMB) and natural graphite powder is used as theelectrode active material in the slurry composition.

The amount of the active material used is not specifically restricted,but it should be enough to provide capacitance needed without affectingprocessing properties of the electrode film. In one embodiment, theamount of the active material is 20 to 80 wt % based on the total weightof the composition.

The conductive additive of the composition may be, but not limited to,at least one of granular graphite KS4 (4 μm), granular graphite KS6 (6m), vapor grown carbon fiber (VGCF) and particular carbon black (SP).Preferably, the conductive additive is vapor grown carbon fiber (VGCF).

A functional group can be introduced to the conductive additive bysurface treatment such that the conductive additive has a double-bondfunctional group for reacting with maleimide on its surface. Forexample, a siloxane coupling agent or an oleic acid coupling agent canbe utilized to modify the conductive additive so as to make theconductive additive have a vinyl double-bond functional group forreacting with a modified maleimide disperser on its surface. In general,the amount of the conductive additive is 0.1 to 5 wt % based on thetotal weight of the composition.

The binder in the composition may be, but not limited to,poly(vinylidene difluoride) (PVDF), acrylic resin or styrene-butadienerubber (SBR), and at least one binder can be used. The binder and themodified maleimide disperser can be mixed into a uniform networkstructure to improve the coating properties of the slurry. In oneembodiment, the binder is 0.1 to 15 wt % based on the total weight ofthe composition. The electrode slurry composition may further includeother additives such as surfactants; and a reaction initiator such asperoxides or 2,2′-azobisisobutyronitrile (AIBN).

EXAMPLES Preparation 1 Preparation of a Modified Maleimide OligomerContaining a Free Radical Capture

Bismaleimide (N,N′-bismaleimide-4,4′-diphenylmethane), barbituric acid(BTA) and hydroquinone at a molar ratio of 2.0:1.0:0.2 were placed in areactor containing N-methylpyrrolidone (NMP) as a solvent. The ratio ofthe total weight of bismaleimide, barbituric acid (BTA) and hydroquinoneto the weight of the solvent is 20:80. The reaction of the mixture wasperformed at 130° C. for about 3 hours to obtain a modified maleimideoligomer containing hydroquinone.

Comparative Preparation 1 Preparation of Modified Maleimide Oligomerwithout Radical Capture

A modified maleimide oligomer was prepared by the method of Example 1,except that no hydroquinone was added.

Example 1 Preparation of Lithium Ion Battery Containing the MaleimideOligomer of Preparation 1

1087.7 g of lithium cobalt oxide (LiCoO₂), 71.7 g of conductive graphite(KS6), 35.9 g of poly(vinylidene difluoride) (PVDF) and 460 g ofN-methylpyrrolidone were placed into a 3D mixer to form a cathode slurryof a standard lithium ion battery. The maleimide oligomer of Preparation1 was 1 wt % based of the total weight of solid contents added in theslurry composition.

Then, a cathode plate was manufactured according to the standardmanufacture method of a lithium ion battery. 1,860 g of mesocarbonmicrobeads (MCMB 2528), 20 g of conductive graphite (KS4), 120 g ofpoly(vinylidene difluoride) (PVDF), 4.5 g of oxalic acid and 1,451.5 gof N-methylpyrrolidone were placed in a 3D mixer to form a cathode plateslurry which was then coated on a surface of an aluminum foil. A cathodeplate was thus obtained.

Further, anode slurry and an anode plate were manufactured according tothe standard manufacture method of a lithium ion battery. 1,860 g ofmesocarbon microbeads (MCMB 2528), 20 g of conductive graphite (KS4),120 g of poly(vinylidene difluoride) (PVDF), 4.5 g of oxalic acid and1,451.5 g of N-methylpyrrolidone were placed in a 3D mixer to form ananode plate slurry which was then coated on a surface of a copper foil.An anode plate was thus obtained.

Then, the cathode plate and the anode plate were assembled to form astandard battery cell (Jelly Roll, 503759C) having the size of 5 mm(height)×37 mm (width)×59 mm (length). 4.2 g of standard electrolyte(PC/EC(ethylene carbonate)/DEC(diethyl carbonate)=2/3/5 (volume ratio)was charged in the battery cell, and 1.1 M LiPF6 and 2.0 wt % vinylenecarbonate (VC) were added. Then, the lithium ion battery of Example 1was yielded after packaging and aging.

Comparative Example 1 Preparation of Ion Battery without the MaleimideOligomer of Preparation 1

A lithium ion battery was prepared by the method of Example 1, exceptthat the maleimide oligomer of Comparative Preparation 1 was used.

Comparative Example 2 Preparation of Lithium Ion Battery without theMaleimide Oligomer

A lithium ion battery was prepared by the method of Example 1, exceptthat no maleimide oligomer was added.

Test Example 1 Test of Properties of Lithium Ion Batteries

Evaluation of battery properties was carried out under a stable currentprogram at IC discharging/charging rate. The first discharge capacity,the resistance, the discharge residual (the discharged capacity afterthe last charging) after 500 discharging/charging cycles (each includingcomplete discharging in an hour followed by charging for an hour) at theroom temperature, and the discharge residual after 500discharging/charging cycles at 55° C. were recorded during the test, andthe results were listed in Table 1.

TABLE 1 Battery Properties The first resis- 1 C/1 C discharge 1 C/1 Cdischarge discharge ca- tance residual at room residual at pacity (mAh)(mΩ) temperature (%) 55° C. (%) Example 1 1348 30 91 84 Comparative 131033 89 75 Example 1 Comparative 1345 30 86 70 Example 2 Room temperature:20 to 30° C.

Test Example 2 Test of Safety of Lithium Ion Batteries

A needling test was carried out with a needle diameter of 2.5 mm and aneedling speed of 1 mm/S to determine safety of the batteries. Theresults were listed in Table 2.

TABLE 2 Bursting Central Temperature into flames at needle (° C.)Example 1 No 135 Comparative No 145 Example 1 Comparative Yes 701Example 2

In light of Table 1 and Table 2, the lithium ion battery prepared from amodified maleimide oligomer containing a free radical capture hassafety, high capacitance, and excellent cycle life at both roomtemperature and high temperature.

The examples aforementioned are used only to illuminate the mechanismand effects of the disclosure, and have no trend to limit the disclosurein any means. Those skilled in the art can modify the examples withoutdeparting from the spirits and scopes of the disclosure. Thus, what isclaimed by the disclosure are as following claims.

What is claimed is:
 1. A method for preparing a modified maleimideoligomer for a battery, comprising the step of: performing a reaction ofa compound having a barbituric acid structure, a free radical capture,and a compound having a maleimide structure, wherein a molar ratio ofthe compound having the maleimide structure to the compound having thebarbituric acid structure is in a range of from 25:1 to 1:1, and a molarratio of the compound having barbituric acid structure to the freeradical capture is in a range of from 1:1 to 1:0.1.
 2. The method ofclaim 1, wherein the compound having the barbituric acid structure hasis a compound of formula (I):

wherein X, Y and Z are all oxygen atoms or at least one of them isreplaced with a sulfur atom, and R₁, R₂, R₃ and R₄ are eachindependently hydrogen or C₁₋₅alkyl.
 3. The method of claim 2, whereinX, Y and Z are all oxygen atoms, both R₃ and R₄ are hydrogen, and R₁ andR₂ are each independently hydrogen or C₁₋₅alkyl, provided that R₁ and R₂are not hydrogen at the same time.
 4. The method of claim 1, wherein thefree radical capture is at least one selected from the group consistingof hydroquinone, α-tocopherol, bisphenol-A, phenol, p-benzoquinone,1,4-dihydroxynaphthalene, p-methoxyphenol (MEHQ), dodecanethiol,butanethiol, carbon tetrachloride, carbon tetrabromide, catechol,resorcinol, methyl-hydroquinon, trimethylhydroquinone,tert-butylhydroquinone and 2,5-di-tert-butyldroquinone.
 5. The method ofclaim 1, wherein the compound having the maleimide structure is acompound of formula (II):

wherein each of m, n and o is an integer greater than
 1. 6. The methodof claim 1, wherein the compound having the maleimide structure is acompound of formula (III):

wherein R is C₁₋₁₂alkylene,


7. The method of claim 1, wherein the compound having the maleimidestructure is at least one selected from the group consisting ofphenylmaleimide, N-(p-methylphenyl) maleimide, N-(o-methylphenyl)maleimide, N-(m-methylphenyl)maleimide, N-cyclohexyl maleimide,maleimide, maleimidophenol, maleimidobenzocyclobutene,phosphorus-containing maleimide, phosphonate-containing maleimide,siloxane-containing maleimide,N-(4-tetrahydropyranyl-oxyphenyl)maleimide and 2,6-xylyl-maleimide.
 8. Amodified maleimide oligomer for a battery, which is produced by themethod of claim
 1. 9. A composition for a battery, comprising: an activematerial; a conductive additive; a binder; and the modified maleimideoligomer produced by the method of claim 1 in an amount of 0.1 wt % to 5wt % based on a total weight of solid contents in the composition. 10.The composition of claim 9, wherein the active material is a cathodeactive material or an anode active material.
 11. The composition ofclaim 10, wherein the cathode active material is at least one selectedfrom the group consisting of lithium nickel cobalt aluminum, lithiumnickel cobalt manganese, lithium cobalt oxide, lithium manganese oxide,lithium nickel oxide and lithium ferric phosphate oxide.
 12. Thecomposition of claim 10, wherein the anode active material is at leastone selected from the group consisting of mesocarbon microbeads andnatural graphite powder.
 13. The composition of claim 9, wherein theactive material is in an amount of 20 to 80 wt % based on the totalweight of the composition.
 14. The composition of claim 9, wherein theconductive additive is at least one selected from the group consistingof granular graphite KS4, granular graphite KS6, vapor grown carbonfiber, and particular carbon black SP.
 15. The composition of claim 9,wherein the conductive additive is surface-treated to have a functionalgroup with a double-bond.
 16. The composition of claim 9, wherein theconductive additive is modified by a coupling agent to have a vinylgroup.
 17. The composition of claim 16, wherein the coupling agent is atleast one selected from the group consisting of a siloxane couplingagent and an oleic acid coupling agent.
 18. The composition of claim 9,wherein the conductive additive is in an amount of 0.1 to 5 wt % basedon the total weight of the composition.
 19. The composition of claim 9,wherein the binder is at least one selected from the group consisting ofvinyl difluoride, acrylic resin and styrene-butadiene rubber.
 20. Thecomposition of claim 9, wherein the binder is in an amount of 0.1 to 15wt % based on the total weight of the composition.